[TEST-ONLY] Make caching tests to require Xcode26

Add compilation caching test requirement to be Xcode26 to workaround
issues in older compiler versions.

Author: cachemeifyoucan

Tests/SWBBuildSystemTests/ClangCompilationCachingTests.swift

@@ -19,7 +19,7 @@ import SWBTestSupport
 import SWBUtil
 
 @Suite(.skipHostOS(.windows, "Windows platform has no CAS support yet"),
-       .requireDependencyScannerPlusCaching, .skipInXcodeCloud("flaky tests"))
+       .requireDependencyScannerPlusCaching, .skipInXcodeCloud("flaky tests"), .requireXcode26())
 fileprivate struct ClangCompilationCachingTests: CoreBasedTests {
     let canUseCASPlugin: Bool
     let canUseCASPruning: Bool

Tests/SWBBuildSystemTests/ClangModuleVerifierTests.swift

@@ -192,7 +192,7 @@ fileprivate struct ClangModuleVerifierTests: CoreBasedTests {
     }
 
     @Test(.requireSDKs(.macOS), .requireClangFeatures(.wSystemHeadersInModule), .requireDependencyScannerPlusCaching,
-          .skipInXcodeCloud("flaky tests"))
+          .skipInXcodeCloud("flaky tests"), .requireXcode26())
     func cachedBuild() async throws {
         try await withTemporaryDirectory { (tmpDirPath: Path) in
             let archs = ["arm64", "x86_64"]

Tests/SWBBuildSystemTests/SwiftCompilationCachingTests.swift

@@ -20,7 +20,7 @@ import SWBTaskExecution
 import SWBProtocol
 
 @Suite(.requireSwiftFeatures(.compilationCaching),
-       .skipInXcodeCloud("flaky tests"))
+       .skipInXcodeCloud("flaky tests"), .requireXcode26())
 fileprivate struct SwiftCompilationCachingTests: CoreBasedTests {
     @Test(.requireSDKs(.iOS))
     func swiftCachingSimple() async throws {